1. Field of the Invention
The present invention concerns a drive train including an internal combustion engine (“ICE”) coupled to a transmission having an opening, and, more particularly, concerns an electric motor and transfer device coupling the electric motor to the transmission via the opening, enabling the electric motor to selectively power the drive train during at least certain intervals when the ICE is powered off.
2. Description of Related Art
In certain circumstances, trucks powered by ICE's idle for long intervals and sporadically move. This may occur, for example, while waiting at ports and other staging areas. Moreover, it may occur for both picking up and dropping off loads and, likewise, for both entering and exiting a staging area. This use of ICE's is in some ways undesirable. The fuel usage and emissions of heat, noise and exhaust in these situations are very large relative to the distances that loads are moved. However, an economically feasible alternative has not been developed, particularly for loads handled by heavy duty, tractor-trailer trucks.
It is, of course, known to use an electric motor in a relatively small hybrid electric vehicle (“HEV”) to assist an ICE or even briefly preempt the use of an ICE for traction, i.e., moving the vehicle. There are, however, numerous obstacles to the use of electric motors, particularly for applications such as described above for trucks. For example, the loads for trucks in staging areas are potentially much greater than what is encountered by conventional HEV's.
While it does not address all these matters, U.S. Pat. No. 5,558,588 (“Schmidt”) illustrates how an obstacle regarding rotational load transfer has been addressed in the context of HEV's. As Schmidt illustrates, a hybrid transmission for an HEV includes an electric traction motor and planetary gear set within the hybrid transmission housing for transferring rotation from the electric motor to the transmission output shaft, which may also be driven by the ICE. Even with regard to merely this one obstacle, the teachings of Schmidt may be of limited use for the problem described herein above and similar problems. That is, in order to apply the Schmidt arrangement for powering a conventional ICE vehicle via an electric motor, the vehicle's conventional transmission is replaced with the hybrid transmission. Since there are a multitude of trucks currently in service, this approach does not provide a practical transition to the use of electric motors for this service.
In another prior art arrangement that addresses sporadic and relatively slow movement, U.S. Pat. No. 6,269,713 (“Ohke”) discloses the addition of a conventional power takeoff (“PTO”) device to a passenger vehicle in order to take power out of the vehicle's ICE for “inching.” Ohke further discloses the addition of a hydraulic pump, hydraulic motor and secondary transmission coupled to the vehicle's conventional transmission output shaft in order to return power from the PTO for moving the vehicle in the inching mode. While this arrangement does not require replacement of the vehicle's original transmission, it has other disadvantages, not the least of which is that the ICE operates full-time in order to supply power to the PTO for inching. Also, power losses through the hydraulic pump, hydraulic motor and secondary transmission are substantial.
Referring to prior art FIG. 1A, details are shown of a conventional PTO arrangement such as may apply to the Ohke patent. A transmission 122 has a case 127 defining a port 124, which is covered by a removable access plate 121. Internal combustion engine (“ICE”) crankshaft 110 connects to transmission input shaft 125 via clutch 120. In other words, ICE is coupled via crankshaft 110 to a drive train that includes clutch 120 coupled to input 125 of transmission 122.
Transmission 122 has a transfer gear 130 coupled to input shaft 125. As shown in prior art FIG. 1B, a conventional power takeoff (“PTO”) 140, which is a type of transfer device, has a case 142 defining an opening that matches port 124. Case 142 is adapted for bolting to transmission case 127 so as to align case 142 with port 124 so that gear 141 of PTO 140 engages gear 130 of transmission 122, as is conventional. This arrangement conventionally enables takeoff of power from ICE crank shaft 110 via PTO shaft 143.
U.S. Pat. No. 2,923,171 (“Jedrzykowski”) also discloses the use of a PTO for very slow speed operation. In the teaching of Jedrzykowski, the application is for a tractor and the slow speed operation is referred to as “creeping.” According to Jedrzykowski, the tractor's clutch is disengaged for the creeping mode of operation and the PTO is used to put power into its transmission shaft from an externally mounted electric motor. The electric motor is energized by a generator that is, in turn, driven by the tractor's ICE. As in the teachings of Ohke, Jedrzykowski's disclosure only addresses a limited set of obstacles with regard to the present problem and also has the disadvantage that operation of the ICE ultimately supplies the power for creeping, so that the ICE must operate full time.
Thus, it should be appreciated that a need exists for a way to reduce fuel usage and emissions of heat, noise and exhaust in connection with the use of ICE's for idling or for moving short distances or at relatively slow speeds. The need is especially acute for hauling large loads by heavy duty, tractor-trailer trucks, particularly in situations such as in heavy traffic or around staging areas, where movement may be sporadic or relatively slow.